Synthesis of Gold Nanoparticles Via Chemical Reduction of Au (III) Ions by Isatin in Aqueous solutions: Ligand Concentrations and pH Effects


Synthesis of gold nanoparticles (GNPs) from the reduction of tetracloroaurate(III) (AuCl4-) anions by isatin (1H-indole-2,3-dione) was achieved in aqueous solution without the use of reducing nor dispersing agents and GNPs were characterized by UV-visible absorption spectroscopy, SEM, TEM, AFM and X-ray diffraction (XRD) and FTIR analyses . The reduction process was monitored with time by measuring the UV-visible spectra of the nanoparticle solutions at different ligand concentrations and pH values. Concentrations of isatin varied from 0.034- 0.476 mM. Reduction of the Au(III) ions to form stable spherical GNPs with high extinction surface plasmon band (SPB) in range of λ 530-535 nm was found to increase with increased concentration of isatin from 0.170- 4.76 mM. The effects of pH (2.4-11.85) on the rate of synthesis, stability, morphology and particle size of GNPs were also studied spectrophotometrically. Best results were obtained at pH 5.8.